Improvement in meridian-finders



. NITED STATES PATENT FFICE.

WM. STAOKPOLE, OF BROOKLYN, NEW YORK.

IMPROVEMENT IN MERIDIAN-FINDERS.

Specification forming part of Letters Patent No. 50, l S2, dated September 26, 1865.

To all whom it may concern.- i

Be it known that I, WILLIAM STAGKPOLE, of Brooklyn, county of Kin gs, and State of New York,have invented a new and usefulImprovement 1n Surveyors Instruments, which I call a Meridian-Finder; 7 and I do hereby declare that the following is a full, clear, and exact description of the construction and operation of the same, reference being had to the annexed drawings, making a part of this specification.

My invention consists of a small reiiector, mounted so as to turn on its axis, its surfaces being parallel to the center line of its axis, which axis shall always be at right angles to the 'line of collimationof the telescope, the mountmgs of the reiiector to be again mounted so as to turn around a center concentric with the line of collimation of the telescope when the finder is attached to the telescope. Figure 1 is a perspective view of a transitinstrument with the meridian-finder attached thereto. Fig. 2 is a side view ot' the nder. Fig. 3 is a top view of the same. Fig.4is an. other side view of the finder, and Fig. 5 is a section of thesame. Figs. 2, 3, 4, and are full-size drawings.

C is the reflector. which it turns.

g is a collar, having a square hole through which the end of the axis passes, fitting the hole when in its proper position.

j' is a nut, which screws onto the end of the axis, and when screwed fast clamps the reector in the desired position. iis a screw operatin g asatangent-screw, and has a movementaround the mounting of the reiiector.

The mounting of the reflector is securely fastened to aplate, O. This plateis constructed so as to turn freely on another plate, E E, around a center concentric with the line of collimation of the telescope.

The two platesOand E are held together by the thimble M, which screws into the plate E, and has a shoulder pressing against plate O.

j is a tangent-screw; h, its clamping-screw, by means of which the plate O is operated. There are adjusting-screws to adjust the reiiector, so that its planes shall be parallel to a line passing through the center of its axis, and also adjustments to adjust its axis to a right angle with the line of collimation of the tele- D, Fig. 5, is its axis, on

scope; but as such kind ot' adjustments are well known I will not further describe them.

The edge of the plate O is divided into (juarter-hour divisions, having an index on the edge of the plate E,the tWelve-oclock division being at a point where aline drawn at right an- Y gles to the axis of the reilector through the line of collimatiou cuts the hour-circle.

The operation of determining the true meridian is as follows, to wit: Thender being secured to theobject end of the telescope in its proper position, as in Fig. 1, and the instrument leveled, turn the reector on its axis to the positionshown in Fig. 2. Set the telescope level by making the index ot' the vertical limb A mark 00, and clamp the telescope. Set the cross-hairs of the telescope on the imageof some prominent object, as R, (about one thousand yards distant,) Fig. 6, and, by means of the horizontal limb B, layo' an angle equal to the an glo of the suns polar distance at the time and place ot' observation. Clamp the instrument at this angle, and, by means of the collar g, turn the reflector on its` axis till the image ot' the object R comes within the telescopic field Then, by means of the tangentscrew t' and clamp-screw k, bring the image of the objectR onto the cross-hairs, and, with the screw f, securely clamp the reiector in its po` sition. Unclamp the telescope and raise the object end of the telescope till the index of the vertical limb A marks the latitude of the place of observation, and clamp it in that position. Turn the plate Otill the index on plate E marks the nearest quarter-hour to the time of making the observation, and clamp the plate in this position. Turn the entire instrument on its principal center, so that the nder shall be toward the north till the image or brightness of the sun comes within the telescopic lield. Then, by means of the tangent-screw j and the tangent-screw operating the instrument on its principal center, bring the image of the sun exactly on the cross-hairs, and the line of collimation of the telescope will be on the meridian.

The angle of the sun-s polar distancebeing correctly iixed by the reflector and the latitude by the vertical limb, it is not necessary to be very exact in setting the index of the hour-circle, as the suns image Vcan be brought onto the crosshairs by the combined movement of th'e instrument on its principalcenter andthe movement of the plate O around the line oi' collimation, and when the image of the sun is exactly on the cross-hairs (the angle of the suns polar distance and the latitudebeingcorrectlyxed) the telescope invariably points to the north pole. The instrument may remain in this position, and by4 turning the plate O around its hour-circle the image of the sun can be kept continually on the cross-hairs, thereby proving the lineof collimation to be coincident with the meridian.

I claim- A meridian-finder, in combination with' a transit or similar surveying-instrument, said finder consisting of a reector mounted on an axis at right angles to the line of collimation of the telescope, and having; a movement around a center concentric with said line of collimation, substantially as described, but I do not limit my invention to any peculiar form of mechanism in constructing and mounting said reflector.

WM. STAGKPOLE.

Witnesses R. STAGKPOLE, J AMES G. MORGAN. 

